The proposed studies will be directed towards elucidating mechanisms of trophic interactions between motor nerves and skeletal muscle; learning more about axonal transport systems in normal and pathological circumstances; and studying the mechanism of neuromuscular disorders including myasthenia gravis. In the first part of the project we will carry out studies of sprouting of motor nerves, and the effect of various factors in eliciting sprouting. We will also explore the effects of disuse on various properties of skeletal muscle. In the second part, we will study the role of axonal transport in certain experimental neuropathies, and in conditions such as regeneration of nerves. In the third part, we will examine the effects of various aspects of humoral and cellular immune mechanisms in the initiation and maintenance of the myasthenic state in man and animals.